The present disclosure relates to a low pass filter. As a technique for improving the communication speed in mobile communication terminals, carrier aggregation has been known in which radio frequency (RF) signals are transmitted and received at the same time using a single communication line formed by collection of a plurality of component carriers (CC) having different frequency bands. According to Japanese Unexamined Patent Application Publication No. 2016-92699, it is reported that, based on uplink carrier aggregation, when a plurality of RF signals of different frequency bands are amplified by a single power amplifier, intermodulation distortion corresponding to distortion characteristics of the power amplifier occurs. An intermodulation distortion signal serves as a spurious component of an RF signal radiated from an antenna, and provides interference to communication in a frequency band to which a CC belongs or an adjacent frequency band. For example, when a signal in a band of about 800 MHz and a signal in a band of about 1.7 GHz are amplified at the same time, a five-order intermodulation distortion signal is generated in a band from about 1535 MHz to about 1615 MHz. As described above, in an operation based on carrier aggregation, generation of intermodulation distortion and harmonic distortion is a factor for a degradation in characteristics.
For example, as a method for reducing intermodulation distortion generated by uplink/downlink carrier aggregation, for example, a method for mounting a low pass filter for attenuating an intermodulation distortion signal at a transmission path for an RF signal is considered.
However, such a low pass filter has a drawback in that unnecessary insertion loss occurs in a transmission path for an RF signal when uplink/downlink carrier aggregation is not implemented.